Rainer Moorfeld

Performance of a multiband impulse radio UWB architecture

In this paper a highly flexible and scaleable multiband impulse radio UWB architecture for high data rates is described and evaluated. The investigations are mainly focused on on-off-keying modulation combined with a low-complexity non-coherent energy detection receiver. Various representative system configurations are defined and examined by simulation, studying effects of pulse generation, filtering, synchronization, demodulation and channel coding.

A Simple and Fast Detect and Avoid Algorithm for Non-Coherent Multiband Impulse Radio UWB

In this paper we present a simple and fast detect and avoid (DAA) algorithm for non-coherent multiband impulse radio UWB. By independent par- allelized interception of all subbands, this algorithm shows a very robust and reliable behavior in the de- tection of narrowband interference such as the IEEE 802.11a wireless LAN (WLAN) standard (1). Thereby, narrowband interference detection is possible during an initialization mode but also during data transmission. The detection is based on a static threshold which guarantees a maximum bit error rate in each subband. If a narrowband interferer is present the transmission is avoided on the corresponding subband and a receiver known initialization sequence is transmitted. Due to the fact that there is a loss in data rate, this approach retains the possibility of using all subbands when no interferer is present. radio UWB system including its capability for narrowband interference mitigation is necessary. This paper presents a simple and novel narrowband interference mitigation technique for non-coherent multi- band impulse radio UWB. The proposed detect and avoid algorithm is based on an extended initial channel estima- tion as well as a recursive channel estimation which is described in (7). Thereby, the estimated values are used to detect a narrowband interferer within the initialization or the data transmission phase. The detection algorithm is very fast and an active narrowband interferer can be detected in less than 250 ns. The disturbed subband will be deactivated and remains off until a new channel estimation is initialized. The accuracy in the frequency domain of the detect and avoid algorithm depends on several system parameters, especially on the number of subbands. This paper is organized as follows: Section II introduces the system model including the non-coherent energy de- tection scheme. In section III we illustrate the impact of a specific narrowband interference source to a multiband impulse radio UWB system. Section IV shows the appli- cation of a static mitigation approach as well as a simple and robust detect and avoid algorithm. Finally, simulation results as well as conclusions are given.

Multilevel PAM with optimal amplitudes for non-coherent energy detection

This paper analyzes multilevel pulse amplitude modulation (M-PAM) for energy detection receivers. Because of the asymmetric, non Gaussian probability density function (PDF) of the energy detected signal, the optimal signal constellation is not known a priori. In order to achieve optimal symbol error rate performance using M-PAM, the optimal signal constellation will be calculated. Finally the SER performance of the energy detection receiver based multiband impulse radio UWB architecture within the IEEE802.15.3 a channel model using M-PAM will be demonstrated.

Performance of coherent and non-coherent receivers of UWB communication

Ultra-wideband (UWB) technology is currently investigated as one viable solution for high capacity short range indoor systems, because of its robustness in dense multipath environment, low cost and low power implementation, and the high bit rates achievable. In this paper we present the performance of coherent and non-coherent UWB receivers and especially for LDR-UWB systems with one of the most complicated application scenarios, under a realistic propagation environment, that takes into account also the effect of path-dependent pulse distortion. As far as coherent receivers are concerned, both maximal ratio combining (MRC) and equal gain combining (EGC) techniques are analyzed, considering a limited number of estimated paths.

A low complex and efficient coexistence approach for non-coherent multiband impulse radio UWB

When bringing a high data rate multiband impulse radio UWB system to the market it has to coexist with other already existing UWB technologies such as multiband OFDM UWB [1]. This paper analyzes the interference impact of a multiband OFDM UWB system on a non-coherent multiband impulse radio UWB system. It is shown that the impact can be so dominant that communication within the impulse based multiband UWB system gets worse. For this reason a static as well as a dynamic coexistence approach are considered. The dynamic approach uses an efficient, robust and easy to realize “pixel” based interference detection algorithm in conjunction with an adapted bandplan array. In comparison to the static approach, the dynamic coexistence approach allows higher data rates during data transmission phases without significant losses in bit error rate performance.

Narrow-Band Interference Robustness for Energy Detection in OOK/PPM

This paper investigates robustness of a non-coherent multi-band impulse radio ultra-wideband communication system with respect to narrow-band interference. A statistical analysis of interference at the energy detector output gives insight into its impact and system dependency. Furthermore, the potential of interference mitigation is shown and verified with respect to the processing gain.

Energy detection with optimal symbol constellation for M-PAM in UWB fading channels

This paper presents optimal symbol constellations for M-PAM with energy detection receiver in fading channels. A significant gain in the symbol error probability can be achieved for medium to large degrees of freedom. We also present closed-form solutions for the symbol error probability in flat, approximated frequency selective and frequency selective fading channels. Independent and correlated fading has been considered. The assumption of Gaussian probability density functions based on the central limited theorem has not been used, because of the inaccuracy for low and medium degrees of freedom.

Closed form expressions for the symbol error rate for non-coherent UWB impulse radio systems with energy combining

In this paper, different energy combining schemes for non-coherent UWB impulse radio systems are analysed. Closed form expressions for the Symbol Error Rate (SER) of Pulse Amplitude Modulation (PAM) using a non-coherent energy detection receiver with energy combining in the AWGN and fading channels are presented. The principle of energy combining is based on the fact that the symbol energy is combined in order to take advantage of the path diversity. Equal Gain Combining (EGC), Weighted Gain Combining (WGC) and Selection Combining (SC) are used as combining schemes, and the performance will be verified in AWGN and lognormal multipath UWB fading channels. Energy detection is also used for the detection of spectrum holes in cognitive radio environments.

Performance of energy detection in NLOS frequency-selective fading channels

A closed-form solution for the bit error probability for an energy detection receiver using On-Off-Keying in a frequency selective multipath fading channel with zero-mean complex-normal distributed fading amplitudes is introduced. Independent and correlated fading are considered. The presented results are valid for for all kinds of frequency selective fading channels, especially ultra wideband channels, where the Gaussian assumption for the decision statistic and the flat fading assumption do not hold.

Treatment of temporary narrowband interference in non-coherent multiband impulse radio UWB

This paper considers low complex interference handling with regard to temporary narrowband interference occurrence within a non-coherent On-Off Keying based multiband impulse radio UWB system. The approach allows a precise and reliable sub-band specific on-line detection of narrowband interferences presence or absence within a packets data phase. Due to the systems instability after detection of interference absence, a decision threshold replacement is applied to correctly demodulate the data packets remaining possibly not interfered data bits. Hence, an increased flexibility with respect to efficient interference handling as well as a significant performance gain can be achieved.